Encapsulation molding equipment of the general kind referred to is disclosed, for example, in U.S. Pat. No. 4,368,168 dated Jan. 11, 1983. As disclosed in this patent, in the process of manufacturing semi-conductor chips, elongated strips, usually made of copper or other conductive metal, and commonly called lead frames are provided. The strips of conductive metal are conventionally fabricated by stamping to form support platforms for the chips and electrical leads extending from each platform in predetermined pattern to the strip boundaries or to narrow cross pieces according to the design of the particular chips to be mounted on the support platforms. As a final step in the manufacturing process, the leads are eventually severed from the cross pieces and the boundaries after the chips are formed on the platforms, encapsulated and ready for testing and shipment.
In encapsulating the chips, an extreme degree of care must be taken to avoid touching by the hands. In the case of modern semi-conductor chips, the static electricity passing through the delicate microcircuitry on account of touching the unprotected chip, as well as the transfer of contaminants from the fingers of workers, may render it nonfunctional. In order to avoid this, considerable care must be taken to eliminate physical handling. This has been accomplished in the past by relatively expensive and complicated molds which have a large number of parts which are difficult to operate and to clean following use and are subject to undue wear and damage. In addition, known molding equipment is adaptable to encapsulation molding on only one size chip requiring separate and rather complicated molds for each size chip or for each size of lead frame strip.
The molds of the invention are intended to be used in conjunction with readily available mold presses of the type manufactured, for example, by the Hull Corp. of Hatboro, Pa., U.S.A. Mold presses of the type described have relatively moveable upper and lower platen members. The upper platen member is provided with a vertically extending cylindrical passageway into which a charge of encapsulating material, such as an epoxy resin, is adapted to be placed. The resin in solid form is heated in a preheating oven prior to its deposit in the passageway so that it is already relatively soft in consistency. The resin is then placed within the cylindrical passageway where it is heated by heating elements extending around the passageway and becomes highly liquid within a relatively short period of time. A piston forces the liquified resin to flow from the bottom of the passageway outwardly through a series of runners to mold cavities for encapsulating objects as is known in the art.